Fuel Pressure Drops Rapidly after Sitting 7 months

[trotterlg]

If you are going with a relay in the trunk, just use a 12 volt relay of some sort, use the present wire for fuel pump power to power up the relay and feed 12 volts from the battery through the relay contacts to the fuel pump. Larry

[AleroB888]

My Walbro pump apparently has a check valve as the electric fuel pressure gauge always reads ~50 psi continuously with the engine off after the pump primes and before start up....

Really, what model is it? I had 3 Walbros including one kit packaged by Racetronix, which is now installed. None of them had check valves. The first 2 failed because of defects the Walbro company admitted they had, and corrected in later production runs.

[Schmieder]

If you are going with a relay in the trunk, just use a 12 volt relay of some sort, use the present wire for fuel pump power to power up the relay and feed 12 volts from the battery through the relay contacts to the fuel pump. Larry

Hey, that's a good idea. I like the way you think.

[pocket-rocket]

Well, not the best flow but it is apparent it has a push behind it. Though, from the fuel filter quick disconnect, pumping fuel at a very slow rate. Roughly 5 minutes plus just to get 3/4 a gallon. It is getting worse though, the flow was greater during the fuel rail test yesterday. It is a trickle flow now and I still have 1/4 tank.

My previous post was more about how it sounded like you had good flow from the lines, but not out of the valve, meaning obstruction in the rails somewhere. As far as the flow... A good pump will fill a 5 gallon bucket in a matter of a minute or two.

[Schmieder]

My previous post was more about how it sounded like you had good flow from the lines, but not out of the valve, meaning obstruction in the rails somewhere. As far as the flow... A good pump will fill a 5 gallon bucket in a matter of a minute or two.

Ha, my pump wasn't anywhere near that amount. I would compare the flow to a Rat taking a piss versus a Gorilla.

Well, I feel better knowing for sure the problem lies in the tank. Better that then an electrical issue........lesser of two evils. It's just a matter of busted knuckles, working on my back under the car. At least I did it once, I can do it again this time with out surprises.

[Schmieder]

Now that I know my pump is dead, after sitting, it seems I may have contamination in the tank. The pump's death seems premature but sitting 7 months with out enough fuel to cover it may have been a major factor.

But now I have to think about flushing the tank. I heard of sloshing around with roofing nails or a chain roughly 5-10 feet long as the abrassive. The tank is only 3-4 years old, I'de hate to think it would need relining. The fuel coming out is crystal clear (i pump only 91-93 octane). So maybe my tank is fine.

If I had contaminant issues, would I be able to see a rusty color tint in the fuel? My fuel is VERY clean looking. Well, well see what is at the bottom of the tank.

Today is a beautiful day, time to get to work on the pump swap soon. I want to pump more fuel out but getting a gallons worth in 15 minutes is crazy. I still have 1/8th a tank left. Not too bad, at least it isn't a full tank....thank God!

[pocket-rocket]

I imagine the fuel would be a different color other than clear. You would also be able to see water separate from the fuel in the bucket if water contamination were the case. I know we could very easy.

[walterdude]

When you've got the car up in the air and pull the filler hose from the gas tank (the short rubber hose between filler neck and gas tank) you should be able to get a smaller hose into the tank and siphon the fuel out. It's worked for my 93 Z34, if I remember yours is similar.....
Hope all goes well,,,
Tom.....

[Schmieder]

When you've got the car up in the air and pull the filler hose from the gas tank (the short rubber hose between filler neck and gas tank) you should be able to get a smaller hose into the tank and siphon the fuel out. It's worked for my 93 Z34, if I remember yours is similar.....
Hope all goes well,,,
Tom.....

I just dropped it with the fuel in it. I used 2 jacks with wood to spread the load. Ends up, the contamination was a deteriorating filter. Pieces of the nylon like material were drawn up into the pump screen and the pump itself. The fuel looked fine and the tank was a little dirty, a few specks but nothing troubling. I still flushed it very well, now it is crystal clear.

Here is a lesson, just because the filter LOOKS clean and IS clean, doesn't mean it's a good idea to reuse it anyways. I made that mistake and it cost me a good pump.

At least I got an ACDelco filter. Pricey but worth it. I always had no problems with ACDelco, great company.

I have fuel pressure now. Going to start it up tomorrow, lost daylight and I don't want to run first start in the dark. Gotta have eyes on the beast while she warms up for the first time after a long slumber.

I wanted to start it up but patience is a priceless value. Besides, I have an HD digital camcorder ready and want a good video of the first start for all of you to view.